Face recognition technology generally works by extracting a face from a photograph, and comparing the extracted face with known faces. Through this comparison, it may be possible to determine whether the extracted face belongs to the same person as the known faces. If the extracted face is found to be sufficiently similar to any of the known faces, then a conclusion is drawn that the extracted face is of the same person as the known face.
While visual face recognition techniques may be able to identify faces in certain circumstances, in many cases visual face recognition techniques are not sufficient to identify a face correctly. The images may be of poor quality, thereby making the features of the face difficult to discern. Two faces that are of different people may look similar to each other, and a visual face recognition process may guess the wrong face. Thus, visual face recognition alone may fail to identify faces correctly in some cases.